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Error.prototype.toString()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨July 2015⁩.

The toString() method of Error instances returns a string representing this error.

Syntax

toString()

Parameters

None.

Return value

A string representing the specified Error object.

Description

The Error object overrides the Object.prototype.toString() method inherited by all objects. Its semantics are as follows:

Error.prototype.toString = function () {
  if (
    this === null ||
    (typeof this !== "object" && typeof this !== "function")
  ) {
    throw new TypeError();
  }
  let name = this.name;
  name = name === undefined ? "Error" : `${name}`;
  let msg = this.message;
  msg = msg === undefined ? "" : `${msg}`;
  if (name === "") {
    return msg;
  }
  if (msg === "") {
    return name;
  }
  return `${name}: ${msg}`;
};

Examples

Using toString()

const e1 = new Error("fatal error");
console.log(e1.toString()); // "Error: fatal error"

const e2 = new Error("fatal error");
e2.name = undefined;
console.log(e2.toString()); // "Error: fatal error"

const e3 = new Error("fatal error");
e3.name = "";
console.log(e3.toString()); // "fatal error"

const e4 = new Error("fatal error");
e4.name = "";
e4.message = undefined;
console.log(e4.toString()); // ""

const e5 = new Error("fatal error");
e5.name = "hello";
e5.message = undefined;
console.log(e5.toString()); // "hello"

Specifications

Specification
ECMAScript® 2026 Language Specification> # sec-error.prototype.tostring>

Browser compatibility

	Desktop					Mobile							Server
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android	WebView on iOS	Bun	Deno	Node.js
`toString`	1	12	1	4	1	18	4	10.1	1	1.0	4.4	1	1.0.0	1.0	0.10.0